Lower medial hamstring activity after ACL reconstruction during running: a cross-sectional study.

Area of Science:

• Orthopedics
• Sports Medicine
• Biomechanics

Background:

• Anterior cruciate ligament reconstruction (ACLR) increases the risk of subsequent hamstring (HS) and ACL injuries in footballers.
• Understanding neuromuscular control post-ACLR is crucial for safe return to sport.

Purpose of the Study:

• To investigate hamstring muscle activation patterns during running in individuals who have undergone ACLR.
• To compare HS activation between bone-patellar tendon-bone (BTB) and HS graft types and with healthy controls.

Main Methods:

• Electromyography (EMG) measured medial and lateral HS activation bilaterally during treadmill running at various speeds.
• 21 male ACLR patients (HS or BTB graft) and 19 healthy controls were assessed approximately 7 months post-surgery.
• EMG signals were normalized to peak activity, comparing stance and swing phases between groups.

Main Results:

• Significantly lower relative peak medial HS activation was observed in the stance phase for all ACLR groups compared to controls.
• Effect sizes for reduced medial HS stance activation ranged from -0.63 to -1.09, indicating moderate to large differences.
• Reduced lateral HS activation in the stance phase was noted only in the BTB graft group (-1.05 effect size).

Conclusions:

• ACLR patients demonstrate significant neuromuscular alterations in hamstring activation during running.
• Reduced medial HS activity during the stance phase post-ACLR may contribute to knee instability.
• These findings highlight potential risks for reinjury and inform rehabilitation strategies for athletes returning to sport.